Heretofore the concept of using a steam aroma generated by wetting a bed of freshly roasted and ground coffee with steam admitted to an extremity of a percolator column has been taught. Thus, procedures have been suggested which call for employing the arts of steam aroma collection to a bed of coffee, whence the aromas are added to coffee extract of typically 40% solids and above, whereafter the blend of aroma and extract would be spray-dried, freeze-dried or otherwise dessicated to a stable moisture. Such art practices have not risen to the level whereat they have been feasible commercially, so far as is presently known.
To explain, prior art procedures employing temperatures in the neighborhood of 200.degree. F. and more have been suggested, steaming temperature being 212.degree. to 270.degree. F. However, when such conditions are practiced in large scale equipment such as multi-train percolators, it has been generally found necessary to employ high steaming pressures in the percolator prior to aqueous extraction to get an acceptable rate of steam aroma recovery. The accompanying high temperatures may unduly degrade the body of roasted and ground coffee for later extraction and in any event provide an inferior quality steam aroma. Attempts previously at practicing a lower steaming temperature than 200.degree. F. through use of vacuum have been totally unsuccessful.
To explain further, the details of such a steam aromatization process is set forth in U.S. Pat. No. 3,132,947 to James P. Mahlmann for Method Of Producing Aromatized Coffee Extract. The Mahlmann process produces a product which on a modest scale will provide the desirable volatile coffee flavor intended, viz. one wherein a distilled volatile organic substances is volatilized by the use of steam. This practice employs a modicum of fluxing and rectification as the steam enters a percolator column and migrates upwardly. The problem with such procedures is that in scaling them to reasonable plant size, they fall short of the mark. The principal art problem has involved the means whereby the water soluble solids of an aqueous extract thereafter produced is effectively combined with desired volatile constituents.
To be sure, treatment in a sufficiently elongated vessel can achieve at times development and rectification of the flavor volatiles and a separation and depletion of co-distilled organic acids. However, when one attempts to practice such a process on a reliable commercial scale in extraction columns having a diameter exceeding substantially 16 inches, significant problems are encountered. Treatment is still required calling for condensation and revaporization of flavor volatiles as set forth in the Mahlmann patent. But means must be provided whereby the aromatic flavor values are recovered without at the same time denigrating the flavor quality of extract subsequently recovered from the roasted and ground coffee itself. When scaling up from the conditions set forth in Mahlmann, condensation and refluxing becomes a problem. Provision of sufficient steam aroma to effect the intended results while at the same time avoiding excessive wetting of the coffee particles, has eluded skilled art workers for decades.